1. Field of the Invention
The invention is a process for electroplating gold.
2. Description of the Prior Art
Gold electroplating procedures are extensively used in a variety of industrial applications. Gold plating is used in the fabrication of jewelry and cosmetic articles as well as industrial articles and electrical devices. In certain applications in electrical devices it is particularly advantageous because of its good electrical conductivity, its chemical and physical stability, and freedom from corrosion. Gold electroplating is extensively used with increasing quantities in recent years as conducting paths and contacts in electrical devices. Because of the high cost of gold, it is economically advantageous to minimize the amount of gold used without significant degradation in device performance. In particular, the high cost of gold as well as time factors involved in gold plating processes makes it highly desirable to extend the useful life of gold plating solutions as much as possible. Another result of the high cost of gold is the desire to be able to predict gold layer thickness with considerable accuracy so that minimum standards can be met without excessive overplating.
With extended use of gold plating solutions it has been found that plating efficiency (amount of gold plated per quantity of electricity) decreases and becomes quite uncertain. In order to meet minimum requirements for a particular gold plating application it becomes necessary to deliberately overplate in order to insure minimum thickness requirements. This procedure is often quite wasteful of gold which is economically undesirable. This uncertainty in predicting gold thickness as the age of the plating solution increases often limits the life of the plating solution and requires more frequent replacement of the gold plating solution.
Various anodes have been described in the literature. Many of these anodes are structurally unsuitable for gold plating (see for example Guiseppe Bianchi et al, U.S. Pat. No. 3,428,544 issued Feb. 18, 1969, and Guiseppe Bianchi et al, U.S. Pat. No. 3,491,014 issued Jan. 20, 1970). Other anodes are used in applications quite different from gold electroplating (see for example Guiseppe Bianchi, U.S. Pat. No. 3,616,445 issued Oct. 26, 1971).